Mitigating the impact of phase steps

Abstract

Method and system are disclosed for preventing phase steps in digital receivers and transmitters that have a controllable gain. The method and system of the invention reduces the number of gain changes by applying hysteresis to the gain control of the receiver or transmitter. For a receiver, the hysteresis is applied with respect to the signal level received at the detector/demodulator. For a transmitter, the hysteresis is applied with respect to the transmit signal level. The hysteresis limits how frequent the gain changes occur so that only signals with amplitudes that exceed or fall below predefined thresholds will trigger a gain adjustment. Small, incremental changes in signal amplitude that lie within the range of the hysteresis will not trigger a gain adjustment.

1 . A method of minimizing the impact of phase steps in a digital receiver having a controllable gain and a detector/demodulator, comprising: 
 defining an upper hysteresis threshold and a lower hysteresis threshold in a dynamic range of the detector/demodulator;    receiving a signal at the detector/demodulator, the signal having a plurality of fluctuations in an amplitude thereof;    reducing a gain of the digital receiver if the amplitude of the received signal is above the upper hysteresis threshold of the detector/demodulator; and    increasing the gain of the digital receiver if the amplitude of the received signal is below the lower hysteresis threshold of the detector/demodulator.    
   
   
       2 . The method according to  claim 1 , wherein the fluctuations in the signal are small, rapid fluctuations similar to those resulting from fast fading of the signal.  
   
   
       3 . The method according to  claim 1 , wherein the gain reduction and the gain increase are substantially equal to each other.  
   
   
       4 . The method according to  claim 1 , wherein the lower hysteresis threshold and the upper hysteresis threshold are selected so as to correspond to an upper limit and a lower limit, respectively, of the dynamic range of the detector/demodulator.  
   
   
       5 . The method according to  claim 1 , wherein the digital receiver is capable of being used in a time-continuous mobile communication system.  
   
   
       6 . The method according to  claim 1 , wherein the digital receiver is capable of being used in code division multiple access system.  
   
   
       7 . A digital receiver having a controllable gain, comprising: 
 a detector/demodulator;    a variable gain amplifier connected to the detector/demodulator; and    a variable gain controller connected to the variable gain amplifier, the variable gain controller configured to: 
 define an upper hysteresis threshold and a lower hysteresis threshold in a dynamic range of the detector/demodulator;  
 receive a signal at the detector/demodulator, the signal having a plurality of fluctuations in an amplitude thereof;  
 reduce a gain of the digital receiver if the amplitude of the received signal is above the upper hysteresis threshold of the detector/demodulator; and  
 increase the gain of the digital receiver if the amplitude of the received signal is below the lower hysteresis threshold of the detector/demodulator.  
   
   
   
       8 . The digital receiver according to  claim 7 , wherein the fluctuations in the signal are small, rapid fluctuations similar to those resulting from fast fading of the signal.  
   
   
       9 . The digital receiver according to  claim 7 , wherein the gain reduction and the gain increase are substantially equal to each other.  
   
   
       10 . The digital receiver according to  claim 7 , wherein lower hysteresis threshold and the upper hysteresis threshold are selected so as to correspond to an upper limit and a lower limit, respectively, of the dynamic range of the detector/demodulator.  
   
   
       11 . The digital receiver according to  claim 7 , wherein the digital receiver is capable of being used in a time-continuous mobile communication system.  
   
   
       12 . The digital receiver according to  claim 7 , wherein the digital receiver is capable of being used in a code division multiple access system.  
   
   
       13 . A method of minimizing the impact of phase steps in a digital transmitter having a controllable gain and a variable gain controller, comprising: 
 defining an upper hysteresis threshold and a lower hysteresis threshold in the variable gain controller;    receiving a transmit signal level at the variable gain controller, the transmit signal level having a plurality of fluctuations therein;    reducing a gain of the digital transmitter if the transmit signal level is above the upper hysteresis threshold; and    increasing the gain of the digital transmitter if the transmit signal level is below the lower hysteresis threshold.    
   
   
       14 . The method according to  claim 13 , wherein the fluctuations in the signal are small, rapid fluctuations similar to those resulting from fast fading of the signal.  
   
   
       15 . The method according to  claim 13 , wherein the gain reduction and the gain increase are substantially equal to each other.  
   
   
       16 . The method according to  claim 13 , wherein the lower hysteresis threshold and the upper hysteresis threshold are selected so as to correspond to the dynamic range of the modulator.  
   
   
       17 . The method according to  claim 13 , wherein the digital transmitter is capable of being used in a time-continuous mobile communication system.  
   
   
       18 . The method according to  claim 13 , wherein the digital transmitter is capable of being used in a code division multiple access system.  
   
   
       19 . A digital transmitter having a controllable gain, comprising: 
 an antenna;    a variable gain amplifier connected to the antenna; and    a variable gain controller connected to the variable gain amplifier, the variable gain controller configured to: 
 define an upper hysteresis threshold and a lower hysteresis threshold in the variable gain controller;  
 receive a transmit signal level at the variable gain controller, the transmit signal level having a plurality of fluctuations therein;  
 reduce a gain of the digital transmitter if the transmit signal level is above the upper hysteresis threshold; and  
 increase the gain of the digital transmitter if the transmit signal level is below the lower hysteresis threshold.  
   
   
   
       20 . The digital transmitter according to  claim 19 , wherein the fluctuations in the signal are small, rapid fluctuations similar to those resulting from fast fading of the signal.  
   
   
       21 . The digital transmitter according to  claim 19 , wherein the gain reduction and the gain increase are substantially equal to each other.  
   
   
       22 . The digital transmitter according to  claim 19 , wherein lower hysteresis threshold and the upper hysteresis threshold are selected so as to correspond to the dynamic range of the modulator.  
   
   
       23 . The digital transmitter according to  claim 19 , wherein the digital transmitter is capable of being used in a time-continuous mobile communication system.  
   
   
       24 . The digital transmitter according to  claim 19 , wherein the digital transmitter is capable of being used in a code division multiple access system.